Field of the Invention
The present invention relates to an organic light emitting diode (OLED) display device and more particularly to a flexible OLED display device being capable of preventing damages on a light emitting diode.
Discussion of the Related Art
Various display devices are currently being used for displaying images. A flat panel display devices, such as a liquid crystal display (LCD) device, a plasma display panel (PDP) and an organic light emitting diode (OLED) display device, are widely researched and used instead of a cathode ray tube (CRT) display device because of their excellent capabilities of a thin profile and light weight.
Among flat panel display devices, since the OLED display device has advantages in a response time, a contrast ratio, a viewing angle and power consumption, the OLED display device is widely researched.
A light emitting diode including an organic emitting layer is very weak to moisture. To prevent the moisture to the light emitting diode and protect the light emitting diode, an encapsulation substrate of glass is attached on the light emitting diode.
Recently, flexible display devices, e.g., a foldable display device, a bendable display device or a rollable display device, were introduced. In the flexible display device, new encapsulation film including an inorganic layer and an organic layer is used instead of the glass encapsulation substrate.
FIG. 1 is a schematic cross-sectional view of the related art OLED display device. As shown in FIG. 1, the OLED display device 1 includes a flexible substrate 10, where a display area AA and a non-display area NA at peripheries of the display area AA are defined, a light emitting diode D on the flexible substrate 10 and an encapsulation film 20 covering the light emitting diode D.
The flexible substrate 10 may be formed of polymer such as polyimide, and the light emitting diode D is formed on the flexible substrate 10.
The light emitting diode D is disposed in the display area AA, and a driving unit (not shown) for driving the light emitting diode D may be formed in the non-display area NA.
Although not shown, the light emitting diode D includes a first electrode, a second electrode facing the first electrode, and an organic emitting layer therebetween. In addition, a switching thin film transistor (TFT) as a switching element and a driving TFT as a driving element are formed in each pixel region and on the flexible substrate 10. For example, the first electrode of the light emitting diode D may be connected to the driving TFT.
The encapsulation film 20 covers the light emitting diode D and corresponds to the display area AA and the non-display area NA. The damages on the light emitting diode D in a condition of high temperature and high humidity are prevented by the encapsulation film 20.
In the encapsulation film 20, an inorganic layer and an organic layer are alternately stacked. For example, the encapsulation film 20 may include a first inorganic layer 22 on the light emitting diode D, an organic layer 24 on the first inorganic layer 22 and a second inorganic layer 26 on the organic layer 24. Namely, the encapsulation film 20 may have a triple-layered structure.
In addition, a barrier film 30 may be attached to the encapsulation film 20 using an adhesion layer 32.
However, when the OLED display device is repeatedly folded, repeatedly bent or repeatedly rolled, there are damages in the light emitting diode D. Accordingly, displaying quality and/or lifespan issues arise in the OLED display device 1 of related art.